It shows existent proof of the animals that used to be alive. We can use these fossils and compare them to today's animals, getting a better picture of what these old animals looked like. We also can figure out relatives and more with them! It also may give ideas of what the earth was like based off how they look. For example, something with long legs, a horn, a long tail ect. Why did these animals need that? It could've been part of a survival tool they used. We can compare the fossil to a animal-relative of today's time, and make good guesses.